Secondary-stage throttle control for a multi-stage carburetor



y 7, 1958 H. A. cARLsoN ETAL 2,836,404

SECONDARY-STAGE THROTTLE CONTROL FOR A MULTI-STAGE CARBUBETOR Filed May3, 1953 2 Sheets-Sheet 1 F'IG.6.

- INVENTOR. HAROLD A.CARLSON BY OLIN J. EICKMANN ATTORNEY y 2 1958 H. A.CARLSON ETAL 2,836,404

SECONDARY-STAGE THROTTLE CONTROL FOR A MULTI-STAGE CARBURETOR Filed May3, 1955 2 Sheets-Sheet 2 INVENTOR. HAROLD A.CARLSON BY OLlN J. EICKMANNATTORNEY United SECONDARY-STAGE THROTTLE CONTROL FOR A NIULTI-STAGECARBURETOR Application May 3, 1956, Serial No. 582,421

8 Claims. (Cl. 261-23) This invention relates to multi-stagecarburetors, and more particularly to the type having each stageseparately controlled by an individual throttle valve wherein theprimary stage throttle is manually controlled, and the secondary stagethrottle automatic in operation.

According to this invention, the separate stages are individuallycontrolled by separate throttles arranged for operation so as to matchthe carburetor capacity with engine requirements. In order to do this,the primary throttle is mechanically interconnected with the automaticsecondary throttle in such a way as to control the init-al opening ofthe secondary throttle with respect to the degree of opening of theprimary throttle and perform a sequential closing operation in which thesecondary throttle is first moved to the full-closed position as theprimary throttle returns from the full-open position.

The automatic secondary throttle is of the type which is so mounted asto be unbalanced to close by the action of suction thereon. Theautomatic opening of the sec ondary throttle is performed by anunbalanced weight acting in the opposite direction to rotate the valveagainst the force of suction.

The objects and advantages of this invention will be -more clearlyunderstood as hereinafter described in the detailed description, takenwith the accompanying drawings, in which:

Fig. 1 is a view illustrating a conventional four-barrel carburetor inside elevation.

Fig. 2 is a view in side elevation of the opposite side of thefour-barrel carburetor shown in Fig. 1.

Figs. 3 and 4 are fragmentary views of the carburetor in Fig. 2, showingthe mechanical gearing between the throttle shafts and illustrating twopositions during operation of the carburetor.

Fig. 5 is a fragmentary view of the carburetor in Fig. 1, showing thegearing on the opposite side and the position of the parts duringoperation of the carburetor.

Fig. 6 is a view in vertical section, taken through the carburetor asshown in Fig. 2, illustrating one of each pair of primary and secondarymixture conduits.

The invention is illustrated as applied to a multibarrel, multi-stagecarburetor of the type commonly referred to as a four-barrel. Thedetails of this type of carburetor are generally shown in many patents;for example, the patent to Carlson et al., No. 2,715,522 of August 16,1955. Since this invention is primarily concerned with a mechanism forcontrolling the operation of the throttles, details of the fuel systemwill not be j'nary mixture conduits 7, and a pair of secondary mix-Patent "Euro conduits 8, only one of each of which is shown,

'conduits 8'.

but, since each pair is identical, a description of one will serve forboth in each instance. Within the air horn section it is ournaled achokeshaft 9 mounting a choke valve 10, which controls the entrance ofthe air horn communicating with the primary mixture conduits or barrels.Within the main venturi 12 is a primary venturi 13. A main fuel nozzle14 opens into the primary venturi 13. It will be understood that thefuel supply within the fuel bowl section 3 communicates with the mainfuel nozzles 14 by way of suitable main fuel passages connecting thenozzles and a metered inlet in the fuel bowl.

The outlet of the mixture conduit 7 is controlled by a throttle valve 15mounted on the throttle shaft 16, which is suitably journaled in thefuel bowl section 3 so as to pass through both of the primary mixtureconduits 7. Adjacent one edge of the throttle 15 are located the usuallow-speed fuel ports 17 and 18, the latter of which is suitablycontrolled by an adjustable needle valve 19 in a manner well understoodin the art. Likewise, these ports communicate with the fuel passage tothe main fuel nozzle 14 through a series of vertical passages 20 and ahorizontal, interconnecting passage 21, all in a manner understood inthe art.

Within the secondary mixture conduit is a main venturi 23 in which isconcentrically arranged a primary venturi 24 having a main fuel nozzle25. This fuel nozzle is also interconnected with the supply of fuelwithin the fuel bowl section 3 by a suitable main fuel passage. Theoutlet of the secondary mixture conduit 8 is controlled by a throttlevalve 26 mounted on a throttle shaft 27 suitably journaled in the fuelbowl section 3 and passing through both secondary mixture Itshould benoted that the throttle valve 26 is unbalanced to be closed by suction,and the degree of unbalance is illustrated by the distance between thecenter line X-X of the secondary throttle shaft 27 and the center lineYY of the secondary mixture conduit 8.

Fig. 2 shows the opposite side of the carburetor illustrated in Fig. l,which, in turn, mounts an automatic choke housing 39 containing asuction and temperature operated mechnism such as shown in the patent toCoffey 2,325,372. The control arm 31 from this mechanism is connected bymeans of a link 32 and arm 33 with the chokeshaft 9. The opposite end ofthe chokeshaft 9 carries an arm 35 connected by way of a link 36 withone end of a lever on the fast idle cam mechanism 37 which is mounted onthe stub shaft 33. Also mounted on the stub shaft 38 is a weighted latchmember 39. A shoulder 41 on the lower edge of the arm 39 abuts one edgeof a dog 41 on a disc-like lever 52 secured to the secondary throttleshaft 27. One end of the lever 39 carries weight W, while the other isformed with a cam follower member 43 positioned for contact by the cam44 formed integral with lever 45 secured to the primary throttle shaft16.

On the end of the lever 45 is an inturned lug 46 positioned to engagethe arm of the fast idle cam mechanism 37 when the primary throttle isopened fully, so as to partially open the choke valve 10 to perform theunloading function.

Primary throttle shaft 16 also carries a suitable actuating lever 43provided with a hole 49 for connection with an actuating rod. A suitablethreaded lug 50 receives an idle set screw 51 for adjusting the closedposition of the primary throttles. Lever 4 8 is connected by way of arod 53 with one end of a pivoted arm 54 positioned to operate theplunger of the accelerating pump 55.

The opposite end of the primary throttle shaft 16, as shown in Fig. 2,has fixed thereto an arm connected by a link 61 in a slot 62 of arm 63freely rotatable on the secondary throttle shaft 27. One face of the arm63,

' position.

Operation 7 When the primary throttles 15 are closed. the secondarythrottles 16 are held closed by the latch 45), 41 at one end of thesecondary throttle shaft 27 and by the engagement between the camsurfaces 70, 71 which hold lever 63 in a position so that face 64 abutsthe lug 65 on the lever 66 at the other end of the shaft 27.

During opening movement of theprimary throttle, the cam faces 70 and 71disengage, as shown in Fig. 3, and the 'end of link 61 in slot62 slidesinto the position engaging the end of the slot 62 so as to hold thesecond- .arythrottles closed. Further movement of the primary throttlemoves the arm 63 so as to disengage face 64 from. lug 65.Simultaneously, cam 44, shown in Fig. 1, engagesinturned lug 43, liftingthe latch arm 39 so as to disengage the abutting'surface 40 from the lug41, all as shown in Fig. 5. This occurs, preferably, after the primarythrottle has reached a point about 10 degrees from wide open.

After the primary throttles have reached this stage in their openingmovement, thesecondary throttles will be unlocked by the mechanismsdescribed on each end of the secondary throttle shaft 27'so as to permitthe weight 67 to open the unbalanced secondary throttles againstsuction. The degree of opening,.however, will be under control of themovement of the primary throttle, as illustrated in Fig. 3.

As the primary throttles 15 move to the wide-open position, arm 63 ispermitted to rotate to the position shown in Fig. 4, which permits fullopening movement of the secondary throttles.

As will be apparent from Fig. 4, when the primary throttles start toclosefrom wide-open position, link 61 initiates closing movementof thesecondary throttles by engagement with the *left end of slot 62.Continued closing of the primary throttles beyond the position shown inFig. 5 disengagescarn 44 from follower 43, permitting the latch '39todrop into engagement with the lug 41 on the secondary throttle shaft.Further closing movement of the primary throttles beyond the positionshown in Fig. 3 engages the face 64 with lugs 65, forcing the secondarythrottles closed 'as the lever 66 and link 61 pass the dead-centerposition. The length of link 61 can be adjusted so that the secondarythrottles are tightly closed at this stage of operation of the primarythrottles. This permits the latch 39 to drop fully into engagement withondary throttles are securely closed on closing of the primarythrottles, and are held 'in that position by mechanism on opposite sidesof the secondary throttle shaft, as well as the action of suction actingupon the secondary throttles 26. This will eliminate any undesirableleakage through the secondary barrels during idling. After the mechanismat opposite ends of the secondary throttle shaft 27 is unlocked, asshown in Figs. 3 and5, the secondary throttles are then free to openunder the force exerted by the weight 67, which opposes the degree ofsuction acting on the unbalanced throttles 26.

On the other hand, the force of suction is sufficient to hold thesecondary throttles tightly closed at idle and in the part-throttlerangeof primary throttle operation,

which means that the primary linkage and throttle re-' turn spring arerelieved of any interference with their operation. In other words, itrequires no force from the primary operating linkage to hold thesecondary throttles closed. Accordingly, it is not necessaryto use anexcessively' strong throttle return spring on the primary.

throttles or adjust the linkage, between the two pairs of throttles inorder to allow the primary throttles to return to the proper positionfor idle when manual pressure on the accelerator pedal is released.

When the choke mechanism is in the on position, the secondary throttleswill normally be locked closed, but full opening movement of the primarythrottle releases the latch 40, 41, permitting the throttles to dropopen, and opens the choke valve simultaneously there- 7 with. e

A structure has been described which will fulfill all the objects andadvantages of the present invention, but 'it is contemplated that othermodifications will occur to those skilled in the, art which come withinthe scop of the appended claims. r

We claim: V g

1; In a multi-stage carburetor, the combination of primary and secondarymixture conduits, a manually controlled primary throttle in said primarymixture conduit, a secondary throttle in said secondary mixture coneduit unbalanced to .close by engine suction, latch means releasable bysaid primary throttle to retain said secondary throttle closed withinthe initialrange .of opening movement of said primary throttle, andbiasing means instantly urging said secondary throttle in an openingdirection upon release of'said latch. g

2. In a multi-stage carburetor, the combination of primary and secondarymixture conduits, a manually controlled primary throttle in said primarymixture conduit, a secondary. throttle in said secondary mixture conduitunbalanced to close by engine suction, biasing locking said secondarythrottle during the initial closing movementof said primary throttlefromfull open position.

3. In a multi-stage carburetor, the combination of primary andsecondary'mixture conduits, a manually controlled primary throttle insaid: primary mixture'conduit, an automatically. operated secondarythrottle in said secondary mixture conduit unbalanced t'o close byengine suction, latch means'for retaining said secondary throttleclosed, mechanism. operatedby said primary throttle dur- 7 ing itsopening 'move'ment to release said .latch so-as to permit said secondarythrottle to open, biasing means urging said secondary throttle to open,and a lost motion linkage means between said'throttles operative duringclosing. of'said primary throttle and, after said latch is freed bysaidprimary throttle operated means, to return said secondary throttle toclosed position.

"4. The combination defined in claim 3, wherein said mechanism includesa lost motion linkage connection between said throttles operating onlyduring part of the closing movement of said throttles, and a positivedriving connection operating during the final closing movementofsaidthrottles. e

5.- In a multi-stage carburetor, the combination of primary andsecondarymixture conduits, a manually con-= trolled primary throttle insaid primary mixture conduit, a secondary throttlein said secondarymixture conduit unbalanced to close by engine suction, a latch to holdsaid secondary throttle closed, means directly connecting with saidsecondary-throttle for urging said secondary throttle open against theforce of suction, means movable with said primary throttle to releasesaid latch, a leyer movable with said primary throttle, 'a second leverfixed on and urging said secondary throttle tojopen, a third leverrotatable with respect to said secondary throttle having a face inabutting relation with said second lever, a slot in said third lever,and a rod positively moved by said first lever and having a lost motionconnection Within the slot in said third lever.

6. The combination defined in claim 5, in which said first lever andsaid third lever have interengaging surfaces in sliding contact formaintaining the abutting surfaces on said second and third levers incontact with one another so as to prevent full opening movement of saidsecondary throttles during part of the range of movement of said primarythrottles.

7. In a multi-stage carburetor, the combination of primary and secondarymixture conduits, a manually controlled primary throttle in said primarymixture conduit, a secondary throttle in said secondary mixture conduitunbalanced to close by engine suction, latch means releasable by saidprimary throttle to retain said secondary throttle closed Within theinitial range of opening movement of said primary throttle, biasingmeans constantly urging said secondary throttle in an opening directionupon release of said latch, a choke mechanism including a choke valveoperatively connected to a rotatable tast idle cam, and means operableresponsive to opening movement of said primary throttle to rotate saidcam and to release said latch for unloading.

8. In a multi-stage carburetor, the combination of primary and secondarymixture conduits, a manually controlled primary throttle in said primarymixture conduit, a secondary throttle in said secondary mixture conduitunbalanced to close by engine suction, latch means releasable by saidprimary throttle to retain said secondary throttle closed within theinitial range of opening movement of said primary throttle, biasingmeans constantly urging said secondary throttle in an opening directionupon release of said latch, a choke mechanism including a choke valveoperatively connected to a rotatable fast idle cam, and means operableresponsive to opening movement of said primary throttle to rotate saidcam and to release said latch for unloading, said latch being pivotallyunbalanced to lock said secondary throttle by gravity.

References Cited in the file of this patent UNITED STATES PATENTS2,609,806 Winkler Sept. 9, 1952 2,640,472 Bicknell June 2, 19532,647,502 Braun Aug. 4, 1953 2,752,133 Egerer June 26, 1956

